The natural world. Looking pretty for 3.5b years.

A Tale of Two Rivers

Natural processes like geological weathering and biological evolution will happen wherever similar environmental conditions occur. Two new photographs---one from Earth and one from Mars---show this well.

Rivers that flow across soft ground on broad floodplains produce loops and meanders. They can also occur on uplifted areas like the Colorado Plateau. Geological studies have determined that factors like river bed steepness, erosion resistance of canyon walls, and bedrock structure near the meander all affect its development. Areas on the plateau that were once relatively flat, before the bedrock was uplifted, show the most meanders and loops.

Double Oxbow Loops, Canyonlands National Park, Utah (credit: NASA)

Likewise, the same geological process has been seen on Mars. The Mars Reconnaissance Orbiter has photographed a cutoff meander made by a river that eroded its outer bank, producing a pronounced curve, broke through, and then continued to flow onwards in a different channel. According to NASA, the abandoned channel formed an oxbow lake until it dried away along with Mars. The river's ridges appear as the old channel, but erosion has produced an inverted topography. What was once low, the river bottom, was more resistant to wind erosion and so is now higher rock. Since meandering river systems develop over a long period of time, they tell that Mars was wetter over longer times as well.

Mars River Loops and Meanders (credit: Mars Reconnaissance Orbiter)

Now we need to investigate those extreme ecological habitats that mimic the same environmental conditions to check for life on Mars.